Like the title says what does changing the area in MyDay do besides notifications and areas in the phone app?
It changes what tasks you're able to do and see on the homepage. As I'm signed into Service & Engagement, I can't Fill and Backstock, or do Price Change for instance. I know there's more but that's just off the top of my head. I believe S&E is the only one that limits what you can do as those are all Salesfloor Jobs. Even being signed in to Human Resources and Assets Protection notifications gives you access to those.
There are S&E things you won't see if you aren't logged into that. Do you sales floor people see change requests? How about price audit.
It also changes what areas you will answer for the phone.